The present invention relates to a failure diagnostic method and apparatus for equipment, and more particularly to a failure diagnostic method and apparatus for carrying out a failure diagnosis for equipment based on an operating state of the equipment. In addition, the present invention relates to a recording medium in which a program causing a computer system to execute a process in accordance with the method is stored.
For example, as to manufacturing equipment, it is required for the equipment to be stably operated. Thus, it is necessary to watch an operating state of the equipment. Due to watching the operating state of the equipment, a failure of the equipment is detected and a state where the equipment has failed is rapidly detected, so that the stable operation of the equipment can be realized. As a result, products having even quality can be manufactured.
In a conventional watching process for watching the state of the equipment, a detected parameter value of the state of the equipment is compared with a threshold of an alarm point or a fault point. When the detected parameter value exceeds such a threshold, it is diagnosed that the equipment is becoming a failure state or that the equipment has failed.
For example, as to a mass flow controller which is a gas flow control device of semiconductor manufacturing equipment, Japanese Laid Open Patent Application No. 4-350705 discloses that an alarm issuance level is automatically changed when a set level is changed by a valve voltage comparing circuit of the mass flow controller and that a valve voltage corrected based on a flow rate of gas, a pressure and a temperature is compared with a reference valve voltage so that a failure is prevented.
In an actual mass flow controller, as shown by a solid line I in FIG. 6, for example, supposing a normal gas flow, a value of 14SLM (Standard Liter per Minute) is set as the gas flow rate (a set voltage V1). In the middle of a process, supposing a case where the valve voltage increases due to a failure of the mass flow controller, the set value of gas flow rate is changed to 13.5SLM (a set voltage V2). That is, the case where the gas flow rate is set at 14SLM by the set voltage V1 is a normal state and the case where the gas flow rate is set at 13.5SLM by the set voltage V2 is an abnormal state. Since a variation range of the valve voltage in the normal state overlaps with a variation range of the valve voltage in the abnormal state, it is difficult to determine whether the valve voltage varying as shown by a solid line II is normal or abnormal.
In a case shown in FIG. 6, when the gas flow rate is set at 14SLM, the average of the valve voltage is equal to xe2x88x922.66 volts and the standard deviation thereof is equal to 0.063. When the gas flow rate is set at 13.5SLM, the average of the valve voltage is equal to xe2x88x922.62 volts and the standard deviation thereof is equal to 0.067.
A general object of the present invention is to provide novel and useful failure diagnostic method and apparatus for equipment in which the disadvantages of the aforementioned prior art are eliminated and a recording medium in which a program causing a computer system to execute a process in accordance with the method is stored.
A specific object of the present invention is to provide a failure diagnostic method and apparatus which can accurately detects a state where the equipment has failed or a state where the equipment is becoming failure.
The above objects of the present invention are achieved by a failure diagnostic method for diagnosing a failure of equipment based on an operating state of the equipment, the method comprising steps of: obtaining operating state parameters, in time series, which represent the operating state of the equipment; selecting a predetermined number of operating state parameters from among the obtained operating state parameters; calculating a value of a deviation process capability from the predetermined number of operating state parameters every time the predetermined number of operating state parameters are selected; and determining a state regarding a failure of the equipment based on the value of the deviation process capability.
According to such a failure diagnostic method, every time the predetermined number of operating state parameters are selected from among the operating state parameters which have been obtained in time series, the determination regarding the failure of the equipment is carried out based on the value of the deviation process capability calculated from the predetermined number of operating state parameters.
That is, the variation of the predetermined number of operating state parameters is numerically represented using the value of the deviation process capability. Even if the range of the variation in the normal state overlaps with the range of that in the abnormal state, since the variation is numerically represented, the degree of failure of the equipment (normal, becoming failure and has failed) can be represented. Thus, the state where the equipment has failed or is becoming failure can be accurately determined from the operating state of the equipment.
In addition, since the value of the deviation process capability is calculated every time the predetermined number of operating state parameters are selected from among the operating state parameters which have been obtained in time series, the state of the equipment in a period in which the predetermined number of operating state parameters were obtained is determined.
The operating state parameter representing the operating state of the equipment includes various kinds of control parameters for controlling the equipment (a set voltage used to set a gas flow rate in a gas flow controller) and detected values, such as the temperature and the driving speed.
To grasp the time variation of the state regarding the failure of the equipment, in the above failure diagnostic method according to the present invention, the predetermined number of operating state parameters which are successive in time series may be shifted on a time scale and selected from among the obtained operating state parameters.
According to such a failure diagnostic method, since the predetermined number of operating parameters which are successive in time series are shifted on the time scale and selected, the time variation of the value of the deviation process capability which is calculated every time the predetermined number of operating state parameters are selected corresponds to the time variation of state of the equipment.
In addition, to grasp the time variation of the state of the equipment at a real time (every time the operating state parameters are actually obtained), in the present invention, every time an operating state parameter of the equipment is obtained, the latest predetermined number of operating state parameters including the obtained operating state parameter may be selected.
According to such a failure diagnostic method, the operating state parameters are shifted by an interval at which the operating state parameter is obtained so that the latest predetermined number of operating state parameters are selected.
The above objects of the present invention are achieved by a failure diagnostic apparatus for diagnosing a failure of equipment based on an operating state of the equipment, comprising: parameter obtaining means for obtaining operating state parameters, in time series, which represent the operating state of the equipment; parameter selecting means for selecting a predetermined number of operating state parameters from among the obtained operating state parameters; calculating means for calculating a value of a deviation process capability from the predetermined number of operating state parameters every time the predetermined number of operating state parameters are selected; determining means for determining a state regarding a failure of the equipment based on the value of the deviation process capability; and output means for outputting information based on a determination result obtained by the determining means.
In such a failure diagnostic apparatus, every time the predetermined number of operating state parameters are selected from among the operating state parameters which are obtained in time series, the determination of the state of the equipment is performed based on the value of the deviation process capability calculated from the predetermined number of operating state parameters. The information based on the determination result is output by the output means.
A user of such a failure diagnostic apparatus can grasp the state of the equipment from the output information.
Further, the above objects of the present invention are achieved by a failure diagnostic apparatus for diagnosing a failure of equipment based on an operating state of the equipment, comprising: parameter obtaining means for obtaining operating state parameters, in time series, which represent the operating state of the equipment; parameter selecting means for selecting a predetermined number of operating state parameters from among the obtained operating state parameters; calculating means for calculating a value of a deviation process capability from the predetermined number of operating state parameters every time the predetermined number of operating state parameters are selected; means for generating information regarding a failure state of the equipment based on the value of the deviation process capability calculated by the calculating means; and output means for outputting the generated information regarding the failure state of the equipment.
In such a failure diagnostic apparatus, every time the predetermined number of operating state parameters are selected from the operating state parameters which are obtained in time series, the information regarding the failure state of the equipment is generated based on the value of the deviation process capability calculated from the predetermined number of operating state parameters. The generated information is then output by the output means.
A user of such a failure diagnostic apparatus determines the state regarding the failure of the equipment (normal, becoming failure or have failed).
Further, to provide a recording medium in which a program causing a computer to execute a process for failure diagnostic of equipment based on an operating state of the equipment is stored, in the preset invention, the program stored in the medium comprises a parameter obtaining step for obtaining operating state parameters, in time series, which represent the operating state of the equipment; a parameter selecting step for selecting a predetermined number of operating state parameters from among the obtained operating state parameters; a calculating step for calculating a value of a deviation process capability from the predetermined number of operating state parameters every time the predetermined number of operating state parameters are selected; and a determining step for determining a state regarding a failure of the equipment based on the value of the deviation process capability.
From the same viewpoint, a recording medium storing a program causing a computer to execute a process for diagnosing a failure of equipment based on an operating state of the equipment comprises: a parameter obtaining step for obtaining operating state parameters, in time series, which represent the operating sate of the equipment; a parameter selecting step for selecting a predetermined number of operating state parameters from among the obtained operating state parameters; a calculating step for calculating a value of a deviation process capability from the predetermined number of operating state parameters every time the predetermined number of operating state parameters are selected; and a step for generating information regarding a failure state of the equipment based on the value of the deviation process capability.